Method and apparatus for manufacturing gas-filled discharge tubes



Z l/LNh G. A. ESPERSEN Filed Oct. 19, 1937 Jan. 31, 1939.

METHOD AND APPARATUS FOR MANUFACTURING GAS-FILLED DISCHARGE TUBES INVENTOR Patented Jan. 31, 1939 UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR MANUFAC- TURING GAS-FILLED DISCHARGE TUBES Application October 19, 1937, Serial No. 169,760

3 Claims.

This invention relates to gaseous type electric discharge devices and more particularly to processes and apparatus for controlling the admission of gases to such devices. 7

In certain devices for example the cold cathode gaseous discharge tubes, it has been the practice of filling the gases at prescribed pressures through the use of manual type controls. I have found that by accurately and automatically controlling the pressure of the inert gas used in the filling operation within predetermined desirable limits of pressure, and by accurately controlling the duration of the gas filling operation, it is possible to fill discharge tubes on the usual automatic exhaust and sealing machines. As a result it is possible to produce great quantities of discharge tubes with a very high degree of uniformity existing between the various tubes.

An object of the present invention is to provide an improved method of filling electric discharge devices such as cold cathode rectifiers, voltage regulators, gas type photocells, gas type triodes, with a gas or vapor which is later employed in the tube to sustain an ionizing discharge.

Another object is to provide an automatic mechanism for controlling with a high degree of accuracy the various factors encountered in the filling of the gaseous devices named above.

A further feature relates to an improved automatic valve whose operation is controlled by a three contact manometer which allows gas to enter within predetermined limits of pressure. Thus the manometer may be adjusted to admit gas at a minimum value of 3 m; m. of mercury pressure and amaximum value of m. m. of mercury pressure.

A further feature relates to the novel organization of an interlocking system of relays which are effective in controlling the fiow of gas so that at no time does the pressure fall below a predetermined minimum value or does the pressure rise above avpredetermined maximum value of pressure.

Other features and'advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

While the invention will be described herein as embodied in one well-known type of exhaust and sealing machine it will be understood that it is equally applicable to other forms of exhaust and sealing machines. Furthermore, inasmuch as automatic exhaust and sealing machines for lamps, radio tubes, and the like are quite wellknown in the art, the drawing is intended to be merely diagrammatic as to details of structure of the machine as a whole. Accordingly in the drawins,

Fig. 1 is a schematic diagram of certain parts of any well-known form of automatic exhaust machine embodying the invention.

Fig. 2 is a detailed composite schematic diagram of the devices and circuits used in conjunction with the automatic exhaust machine to eiIect the gas filling.

Referring to Fig. 1, there is schematically illustrated an automatic exhaust machine such for example as illustrated in detail in Patent No. 996,936. In general, the machine includes a rotatable spider carrying a series of arcuate hollow sectors I, 2 and 3 each sector being provided with a plurality of ports 4 to receive the tubes to be processed. The spider isrotated in a step-bystep manner in the direction of the arrow by any suitable mechanism, for example by the Geneva gear 5, which is operated from the main driving motor 6, it being understood that the Geneva movement has the same number of teeth as the number of ports 4. Each of the ports 4 is connected by suitable piping to the central rotary valve designated generally by the numeral 1 the rotary valve being provided in the well-known manner with a series of ports equal in number to the ports 4 so that as each tube is advanced to successive positions the particular processing for that position is effected. In the particular machine illustrated the tubes are indexed to twenty four successive positions which are indicated in the drawing by the numerals 1 to 24 inclusive. In positions 1, 2, 3 and v4 the ports 4 are either opened or closed, depending upon the type of tube to be processed. In positions 5 to inclusive the ports are connected through a rotary valve 1 with the first exhaust pump. In position 6 the tube is tested for leaks by any well-known mechanism. From positions 6 to there is provided a suitable oven for baking out the glass and other parts of the tube. In positions 12 to 22 inclusive the tubes are connected to the final exhaust pump and while passing from positions 12 to 23 the various operations are performed. Suitable lighting arrangements are provided in positions 1 to 4 inclusive and 15 to 23 inclusive which may be used for degassing the filaments of types having filaments. In the case of cold cathode or non-thermionic type tubes this latter feature is not necessary. In position 24 the automatic gas filling mechanism (Fig. 2) operates to admit the inert gas (preferably argon, neon, or helium or suitable mixtures of these gases) at a pressure 66 tered the tube. For convenience of understandmg, the sequence of operations may be according to the following schedule:

g Gas filled rectifier wa h vin filaments pened-tube loading Lighting positions D0. Manifold Leak detector Manifold 0. Single pump Exhaust pump Position in oven Lighting positions 0. Sin le pump-getter flash coil Glo sedgas filling-tip oif Gas filled cold cathode types (no filaments) Olosed-tube loading Closed D0. D0. Manifold Leak detector Y Manifold Do. Exhaust pump Do. I Do. Do. Single pump Position in oven Do. Single pump-bombarding coil Single pump Single pump-bombarding coil Single pump Single pump-bombarding coll Single pump Single pump-getter flesh coil Closed-gas fllling-tip oif The above exhaust schedules may be varied considerably in accordance with the various technics known in the art of radio tube manufacture. Other schedules have been found to be equally as desirable as the above but the above schedules are the preferable ones.

Referring to Fig. 2, a detailed description will now be given of the apparatus which comes into operation as the tube reaches position 24.. Port number 24 is connected by a piping system preferably of Pyrex glass tubing to the gas supply tank 25, containing the desired inert gas, vapor or mixture of gas and vapors, whose pressure is to be set between a minimum and maximum value by the controls to be described; Preferably the gas from source 25 is a pure inert gas or gases,

. and the pressure of the supply,tank is controlled side arm 33.

amaeso associated therewith amanually adjustable constriction control device or clamp 26, and a similar electromagnetically controlled constriction device 29. These devices are provided with suitable pinching jaws which when moved towards each other control the effective opening through the rubber tubing. By means of the manually adjustable device 26, the desired flow of gas is controlled. The electromagnetic valve 29 is provided with an operating electromagnet 29a which when energized, effects a complete closure of the tubing 21. A similar electromagnetic valve 28 is associated withthe rubber tubing 28a which connects the apparatus to the vacuum pump (not shown). The valve 28 is provided with an electromagnet 28b which is energized from the electrical supply line through the switches 30, 3|.

Associated with the system is an indicating mercury manometer comprising a bulb 32 and a Three contacts 34, 35, 36 are sealed into the manometer and a suitable quantity of liquid mercury is provided within the manometer, the level of the mercury being normally below the contact 35. As the pressure of the gas flowing through the system increases it causes a corresponding rise in the mercury in the arm 33 thus connecting the contacts 35, 36 successively in circuit. The manometer is sealed to the glass tubing of the system as indicated, and connected in the system is a suitable Geissler tube 31 having the usual electrodes 33, 39, whereby the proper gases enter the reservoir 4|. The reservoir 4| is s of sufficient capacity to stabilize the pressure in the system whereby the number of relay contacts required is at a minimum. For the purpose of controlling the gas supply valve 29, there are provided a pair of relays 42, 43, and for the purpose of energizing the Geissler tube there is provided a high voltage transformer 44. the primary of which is connected to the electric supply line through the switch 45.

Before fllling the system with a gas; it is completely evacuated by closing the valve 26 while maintaining valve 28 open. When the system has been properly exhausted, the valve 26 is opened and the gas flows through tube 21, tube 31, trap 40 and into the reservoir 4|. As the pressure in the system rises, the mercury in the manometer 32 rises until a connection through the mercury is made between contacts 34 and 36. Under these conditions, acircuit is completed from the supply line 46 through the winding of relay 43, conductor 41,- contact 36, contact 34 to line conductor 48. Relays 42 and 43 are preferably of the volt A. C. operating type. Relay 43 when thus energized operates its armatures 43, 50 away from the associated back contacts 5|, 52 and into engagementwith the respective front contacts 53, 54. Armature 49 when it engages contact 53 connects the neon lamp indicator 55 in the'line circuit as a visual indication that relay 43 is operated. The engagement between armature 50' and contact 54 completes a circuit from line conductor 46 through the winding of relay 42, contact 54, armature 50, conductor 56, contact 35, contact 34 to line conductor 48. Relay 42 when thus energized moves its armatures 51 and 58 away from the associated back contacts 61, 62 into engagement with respective front contacts 53, 60.

a,ics,sso

able from'the line conductor 48, windingot relay 42, contact 59, armature 51, conductors N,- 8!, contacts 35, u to line conductor ll. Relay I2 therefore remains operated so long as the pressure in the system is sufilcient to maintain the merwry at the level of contact 35; Thus contact II controls the minimum pressure of gas in the system and contact 38 controls the maximum pressure oi 15 gas in the system, it being understood of course that these two contacts are so positioned and the dimensions of the manometer are such that the desired maximum and minimum pressures are controlled.

Should the pressure in the system drop below the minimum, as for sample when a tube to be filled reaches port II. the level of the mercury in the manometer drops below the contact 35. Under these conditions the clrcuit z for relay is broken and the previously described locking circuit for relay 2 is also broken causing the release or both these relays. The release otrelay l2 causesthe valve 2! to be reopened thus admitting gas to the'required presso sure into the system. Bhouldthepressure'inthesystem rise above the predetermined maximum the operating circuit for relay 0 is again closed as described above thus preventing further entry oi gas into the system.- Relay 4! may also have associated therewith through contacts I and II a neon lamp indicator ii to indicate the condition of relay 42. Thus an attendant is able to determine from the sequence of operations of the lamps 8i and I whether the control system is functioning properly. Preferably a condenser "is connected across the contacts II and I to reduce sparking thereat and likewise condensers 00,. are provided across the manometer contacts for a similar purpose. with the tor soing'typeotcontrohitispossihle .to an lamps. radio tubs and the like, with inert gas'between accurately new a pressure thus enabling such devices to be produced in large quantities with -uniformity between the difi'erentlampsortubaandbyemployingany well known exhaust machinesuchtor example as tube'orlamphasbeenfilledwithgasasabove describedtheusualexhausttubulationaboveis sealed-ofifandthetubeisremovedtrmnthemchineinanywellknownmannenitbeimunderstoodthattheabovedeserlbedmleotopsratlcns isrepresentedioreachtubethathloadsdmto Various changes and may be ,3 madehereinwithoutdepartingiromthespirit and scope of the invention. What I claim is:

1. In an automatic exhaust machine or the character described, the combination of a platform to carry a bulb having a plurality of electrodes, means to index said platform in a stepby-step motion to a plurality of successive positions, means eiiective in one of said positions to admit an inert gas into said bulb at a pressure between a predetermined upper limit and a predetermined lower limit, the last-mentioned-means including a mercury manometer'having an upper and a lower contact corresponding respectively to said upper and lower limits, a first relay energized only when the mercury engages said upper contact,'a secondrelay initially energized only when the first relay isoperated and the mercury engages said lower contact, a locking circuit for said second relay independent of the first relay but controlled by said lower contact, and a valve for controlling the admission of the inert gas into the bulb, said valve being controlled conjointly by said pair of relays.

2.-In an automatic exhaust machine of the character described, the combination of a platform to carry a bulb whichis to contain a filling of an inert gas, means to index said platform in a step-by-step motion to a plurality of successive positions, means effective in one of said positions to admit an inert gas into said bulb at a pressure between a predetermined upper limit and a predetermined lower llmit, the last-mentioned means including a mercury manometer having upper and lower contacts corresponding respectively to said upper and lower limits, and an intermediate contact, a first relay energised only when the mercury engages said upper contact. a second relay initially energized only when the first relay I to admit the inert sas into said bulb at a pressure between a predetermined upper limit and a predetermined lower limit, the last-mentioned meansincludingapressureresponsiverelayhaving three contacts, two of which correspond respectively to the upper and lower pressure limits, apairoi'relaysoperated whenacircuitisclosed throughsaidtwocontacmalockingcircuitior one of said relays controlled conlointly by the otherrelayandthethirdcontacaand avalveior controllingtheadmissionoitheinertgasintothe bulb, said. valve being controlled coniointly by said pair or rel!!!- GIORGI A. 

